Vitamin D deficiency in Koreans is serious
Why do Koreans have low levels of vitamin D in the blood?
Vitamin D is not found in many common foods. It is found in blue fish, mushrooms, milk, butter, eggs, etc., but at an insignificant level. The foods with the highest vitamin D content per gram are liver and other animal organs. Primitive man had no reason to be deficient in vitamin D. Primitive man ran bare skin in the sun, hunted animals, and ate their entrails whole. However, modern people do not like to expose their skin to the sun for cosmetic reasons or because of skin cancer.
In the US, it is said that direct sunlight is the best...
The U.S. National Institutes of Health recommends direct exposure of the face or limbs to sunlight between 10:00 am and 3:00 am, at least twice a week, for at least 20 minutes at a time without applying sunscreen. In this case, about 200 IU of vitamin D is produced. Exposure to sunlight enough to cause erythema in midsummer can produce 10,000 IU of vitamin D, but prolonged exposure to strong ultraviolet rays is not good for skin health. In summer, it is recommended to get in the sun 2-3 times a week, before 11am or after 4pm. However, this is a level that prevents vitamin D deficiency.
However, UV cream prevents this!
Even if the sun protection factor (SPF) of sunscreen cream exceeds 80,000, vitamin D synthesis in the skin hardly occurs. However, the sunscreen you use should be at least SPF 15 or higher. In addition, vitamin D synthesis occurs through UVB, which has a shorter wavelength than UVA, which has a longer wavelength. UVB rays do not pass through glass, so vitamin D cannot be synthesized when exposed to sunlight indoors confined to glass. After all, it means that it is difficult for modern people to synthesize enough vitamin D through the skin.
In addition, dietary intake of vitamin D is markedly deficient.
However, you cannot force yourself to eat the intestines of an animal. Butter is high in saturated fat, so I don't like to eat it, and I can't eat dairy products because it hurts my stomach. Shiitake mushrooms, which are known to be rich in vitamin D, are rarely sun-dried these days, and most are hot air-dried. Hot air dried mushrooms contain less vitamin D. Vitamin D loss also occurs during cooking and blanching. Therefore, unlike other vitamins, the intake of vitamin D through food is only about 100 IU, about 10 to 20% of the daily recommended amount.
Severe vitamin D deficiency in modern people
Thus, vitamin D deficiency in modern people is at a serious level. The United States has fortified cereals and milk with vitamin D for the prevention of rickets over 20 years ago. Despite these efforts, Americans still have low levels of vitamin D in their blood. According to the National Health and Nutrition Examination Survey of the United States, in 2010, 42% of Americans had a vitamin D blood level of less than 20 ng/ml.
Especially in Korea...
In our country, the situation is much worse. According to a 2014 survey by the Seoul Institute of Medical Science, 86% of adolescents aged 18 to 20 and 71.1% of the adult population had a vitamin D blood level of less than 20 ng/ml. According to the Health Insurance Review and Assessment Service in 2011, only 16,000 vitamin D deficiency patients were treated by doctors. In 2005, as a result of a multi-center international study conducted by Professor Lim Seung-gil of Yonsei University School of Medicine and others, among adult women in 18 countries around the world, Korean women ranked last in blood vitamin D concentration. Even Korean women were more severely deficient in vitamin D than women in the Middle East who wore chadors all their lives. It may be hard to believe, but in times of starvation, such as the late Joseon Dynasty or the Japanese colonial era, newborns with rickets are often being born in delivery rooms at major university hospitals. This is because Korean women are unable to eat properly through their usual diet and block out sunlight excessively for fear of skin aging. A lack of vitamin D in the mother's blood can lead to crooked bones in the fetus.
People who are prone to vitamin D deficiency
- Elderly people: As you get older, the ability to produce vitamin D in your body decreases rapidly due to the aging of your skin, kidneys, and liver functions. Older adults have up to 75% reduced ability to produce vitamin D compared to younger adults.
- Women, smokers, and those who do not exercise: Women are more likely to be deficient in vitamin D than men, and smokers than non-smokers. Even if you don't exercise well, your vitamin D blood level is inevitably low because you spend less time exposed to sunlight.
- People with kidney and liver disease: Vitamin D is activated in the body through the liver and kidneys, but if you have liver or kidney disease, the activation ability of vitamin D is reduced.
- People who take drugs for a long time: Gastrointestinal drugs added to protect the stomach when prescribing pain relievers, anticonvulsants, and steroids used for rheumatoid arthritis or atopy are typical drugs that cause vitamin D deficiency. Care should be taken to avoid vitamin D deficiency when taking medications containing these ingredients for more than 6 months.
How can I increase my blood levels of vitamin D?
So how much and how should you take vitamin D? First, you need to objectively know your vitamin D blood level. You can usually find out through a blood test at a nearby hospital. If the vitamin D blood level is less than 10 ng/ml, it is a morbid condition in which deficiency such as rickets is a concern, and immediate treatment is required. 10 to 20 ng/ml is not a disease but is classified as unsatisfactory. It is often referred to as deficiency. From 20 ng/ml and above, opinions differ among experts. The most conservative American National Medical Association considers normal if it is more than 20ng/ml and recommends intake of about 600IU per day. The American Endocrine Society says that 30 ng/ml or more is sufficient and recommends 1,500 to 2,000 IU daily. The Vitamin D Association (a non-profit professional organization in California, USA) suggests taking up to 5,000 IU for this, saying that you need to raise it to 50 ng/ml.
My blood level is...
I would like to say that 0 to 10 ng/ml is 'good', 10 to 20 ng/ml is 'good', and 20 to 30 ng/ml is normal but is at the level of 'me'. I think 30~40ng/ml is 'woo', 40~50ng/ml is 'can'. The reason why 40 ng/ml or more is claimed to be 'number' is because many studies have shown that vitamin D's anti-cancer effects need to be 40 ng/ml or more. However, there is no reason to keep it above 50ng/ml. Although there are few side effects, no special benefit has been additionally demonstrated compared to 40ng/ml or more.
According to the National Academy of Medicine vitamin D guidelines...
The criterion for vitamin D toxicity presented by the American National Medical Association is when you consume more than 10,000 IU per day and the blood concentration is more than 200 ng/ml. However, since we need to secure a safe range from normal levels to toxic levels, we recommend taking up to 4,000 IU per day and maintaining blood concentrations within a maximum of 60 ng/ml. As each expert group has a slightly different opinion on this point, it is a good idea to consult with your primary care physician who knows your condition best.
Remember, the dosage is 2,000 IU
A dose of 100 IU is usually required to raise blood levels by 1 ng/ml. If taken now, an increase in blood concentrations will not appear until 3 to 4 months later. I believe that 2,000 IU should be the dose that maximizes the effect while minimizing the possibility of side effects. It has been reported that people who consume 2,000 IU of vitamin D a day and are exposed to sunlight for 10 to 15 minutes reduce their risk of colorectal, breast, and prostate cancer by 50 to 60 percent. In particular, these effects are more pronounced when sufficient vitamin D is consumed during the growth phase than when consumed as an adult.
Daily dosing is also important to maintain concentration.
The 600 IU recommended by the American National Medical Association is too small given the situation in Korea where vitamin D intake is very low. In fact, a large-scale randomized clinical trial at Harvard University School of Public Health in the United States also uses 2,000 IU daily as a rule. When 2,000 IU is administered, the blood level rises by 20 ng/ml . If your vitamin D blood level is 20 ng/ml, which is the standard for determining normal and abnormal levels, it means that if you take 2,000 IU for 3 to 4 months, it will rise to 40 ng/ml. Then at least it's a 'woo'. If your vitamin D blood level is 10 ng/ml, which is the risk level for a deficiency, a dose of 2,000 IU will raise it to 30 ng/ml. This corresponds to the 'Mi' degree level. What you need to be careful about is that even if you reach the target blood level, you need to consistently administer 1,500 to 2,000 IU of vitamin D every day to maintain a blood level of 30 ng/ml for adults. Children and adolescents also need to consume 1,000 IU of vitamin D daily to maintain adequate blood levels.
Vitamin D-only preparations are also a good way
A typical multivitamin contains 100 to 200 IU of vitamin D. Even products that contain a lot are around 400 IU. Therefore, in order to maintain adequate blood levels of vitamin D, it is recommended to take vitamin D-only supplements in addition to multivitamins. According to the National Institutes of Health (NIH), 37% of Americans take vitamin D supplements in the form of supplements. To recap, discuss your vitamin D intake with your doctor, but usually aim for a vitamin D blood concentration of around 30ng/ml, and if you are a little greedy, aim for around 40ng/ml.
How much food should I eat to get 1,000 IU of vitamin D per day?
200ml of milk or yogurt contains approximately 100 to 200 IU of vitamin D. There is about 120 IU of vitamin D in one piece (50 g) of blue fish such as tuna or sardines. The food containing the most vitamin D per unit gram is the wood ear mushroom, which is often used as an ingredient in japchae. Dried throat mushrooms contain 440 μg of vitamin D per 100 g. Most people know that shiitake mushrooms have a lot of vitamin D, but wood ear mushrooms have more vitamin D than shiitake mushrooms.
To get 1,000 IU of vitamin D per day, you need to eat at least 7 to 8 pieces of blue-backed fish every day. You should eat 10 cups of milk or yogurt or 5 to 10 servings of dry cereal daily. Look for mushrooms that have been sun-dried, not hot-air-dried.
Korean men get angry when their wives give them cereal for breakfast because they lack sincerity. However, in terms of vitamin D intake, it is better to eat vitamin D-fortified cereals and low-fat milk than hearty Korean meals prepared with rice, soup, and vegetables.
Esther Lyuh, Doctor of Preventive Medicine, Seoul National University